Opened 9 years ago

Closed 7 weeks ago

#33 closed defect (migrated)

Potential error in CglTwomir

Reported by: jwatson Owned by: somebody
Priority: major Milestone:
Component: Cgl Version: release 0.5.1
Keywords: Cc:

Description

I have isolated a situation in which I believe CglTwomir is returning invalid cuts. I have attached a test driver (driver.cpp), a test input file (mas74.mps, from miplib2003), and the output trace I obtain on our rather vanilla RedHat? linux server.

The “catch” is that I’m using CPLEX 11.2, and the OsiCpxSolverInterface?. Although this technically shouldn’t matter, I suppose (the behavior also occurs with other versions of CPLEX).

A quick summary of the unexpected behavior: 1) The LP relaxation for mas74 solves fine – relaxation is around 10K. Validated with various other solvers. 2) 3 two-mir cuts are found and successfully applied. 3) Upon re-solve after cut addition, the LP relaxation is something like 21K, which is far above the integer optimal of ~11K. Obviously incorrect behavior.

Any help is greatly appreciated – I am seeing similar behavior on a handful of other test instances.

Thanks!

Jean-Paul

Attachments (3)

driver.cpp (1.6 KB) - added by jwatson 9 years ago.
driver.output (12.4 KB) - added by jwatson 9 years ago.
mas74.mps (62.7 KB) - added by jwatson 9 years ago.

Download all attachments as: .zip

Change History (5)

Changed 9 years ago by jwatson

Changed 9 years ago by jwatson

Changed 9 years ago by jwatson

comment:1 Changed 9 years ago by rlh

Forwarded to CglTwomir project manager, Oktay Gunluk.

comment:2 Changed 7 weeks ago by stefan

  • Resolution set to migrated
  • Status changed from new to closed

This ticket has been migrated to GitHub and will be resolved there: https://github.com/coin-or/Cgl/issues/33

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